The present invention pertains to the field of pneumatic-type linear actuators having a body, a chamber in said body that is closed by the end heads, a piston that is arranged in the chamber and is moved by a fluid that is sent alternately to the ends of the piston, and a slide or carriage movable on the body driven by the piston.
Pneumatically actuated rodless cylinders and electric actuators have become known as linear actuators. Particularly, the rodless cylinders have a piston contained in a chamber, in which it slides moved by a fluid fed alternately to the opposite ends of the chamber. The piston drags a body, a carriage or slide, that protrudes on the outside of the chamber for the fixing of a device to be moved. The cylinder must thus be provided with a slot which extends along its generator and which must be closed for sealing by at least one sheet, usually made of metal. However, the slot is a source of air losses, which, combined with the wear of the sheet, limit the output and the life of the actuator.
One object of the present invention is to provide a pneumatic-type, and therefore simple and economical, linear actuator, which does not experience the drawbacks complained about above and which guarantees a better pneumatic sealing, a higher output, and a longer life compared with prior-art actuators.
Another object of the present invention is to provide a pneumatic linear actuator with a motion transmission system from the piston to the slide, which acts as a velocity multiplier and thus which makes it possible for the actuator to be able to be used even in fields in which high performances are required.
The said objects are accomplished with a pneumatic linear actuator of the type mentioned in the introduction, but having the feature of a belt transmitted on pulleys and connecting the piston to the slide, so that a stroke and velocity that are at least twice that of the slide correspond to the stroke of the piston.
In such an actuator, the air losses are practically nonexistent since the sliding chamber of the piston never communicates with the outside. Therefore, a pneumatic seal only on the piston, which can easily be obtained with usual and simple means, such as lip seals, is sufficient.
The control velocity obtainable with this actuator is, with operating conditions being equal, at least twice what can be achieved with the traditional rodless cylinders, in which the carriage is integral with the piston.
Moreover, the actuator proposed also guarantees a longer life, not having parts that can wear out rapidly.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.